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Talk:Rhodophobia/@comment-71.174.57.242-20180402190236/@comment-71.174.57.242-20180402190332
=Anus= From Wikipedia, the free encyclopedia This article is about the bodily orifice. For other uses, see Anus (disambiguation). For details specific to the human anus, see Human anus. The anus (from Latin anus meaning "ring", "circle") is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may include: matter which the animal cannot digest, such as bones;[1] food material after all the nutrients have been extracted, for example cellulose or lignin; ingested matter which would be toxic if it remained in the digestive tract; and dead or excess gut bacteria and other endosymbionts. Amphibians, reptiles, and birds use the same orifice (known as the cloaca) for excreting liquid and solid wastes, for copulation and egg-laying. Monotreme mammals also have a cloaca, which is thought to be a feature inherited from the earliest amniotes via the therapsids. Marsupials have a single orifice for excreting both solids and liquids and, in females, a separate vagina for reproduction. Female placental mammals have completely separate orifices for defecation, urination, and reproduction; males have one opening for defecation and another for both urination and reproduction, although the channels flowing to that orifice are almost completely separate. The development of the anus was an important stage in the evolution of multicellular animals. It appears to have happened at least twice, following different paths in protostomes and deuterostomes. This accompanied or facilitated other important evolutionary developments: the bilaterian body plan, the coelom, and metamerism, in which the body was built of repeated "modules" which could later specialize, such as the heads of most arthropods, which are composed of fused, specialized segments. Contents hide *1Development *2See also *3References *4External links Development Main articles: Protostome and Deuterostome In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. The protostomes were so named because it was thought that in their embryos the dent formed the mouth first (proto–''meaning "first") and the anus was formed later at the opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the dent close up in the middle, leaving openings at the ends which become the mouth and anus.[2] See also *Anal canal *Imperforate anus; a birth defect. *Anorectal manometry References #'Jump up^' Chin, K.; Erickson, G.M.; et al. (1998-06-18). "A king-sized theropod coprolite". ''Nature. 393 (6686): 680. doi:10.1038/31461. Summary at Monastersky, R. (1998-06-20). "Getting the scoop from the poop of''T. rex''". Science News. Society for Science &. 153 (25): 391. doi:10.2307/4010364. JSTOR 4010364. #'Jump up^' Arendt, D.; Technau, U. & Wittbrodt, J. (4 January 2001). "Evolution of the bilaterian larval foregut". Nature. 409 (6816): 81–85. doi:10.1038/35051075. PMID 11343117. Retrieved 2008-07-14. External links *https://en.wikipedia.org/wiki/File:Commons-logo.svg Media related to Anus at Wikimedia Commons Categories: *Digestive system *Anus Navigation menu *Not logged in *Talk *Contributions *Create account *Log in *Article *Talk *Read *View source *View history Search *Main page *Contents *Featured content *Current events *Random article *Donate to Wikipedia *Wikipedia store Interaction *Help *About Wikipedia *Community portal *Recent changes *Contact page Tools *What links here *Related changes *Upload file *Special pages *Permanent link *Page information *Wikidata item *Cite this page Print/export *Create a book *Download as PDF *Printable version In other projects *Wikimedia Commons Languages 89 more *Deutsch *Español *Français *한국어 *Italiano *Русский *Tagalog *Tiếng Việt *中文 Edit links *This page was last edited on 25 February 2018, at 21:49. *Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. *Privacy policy *About Wikipedia *Disclaimers *Contact Wikipedia *Developers *Cookie statement *Mobile view *Enable previews *